Modular cast independent front suspension subframe

ABSTRACT

A suspension and steering subassembly for a heavy truck is provided including a subframe. The subframe includes first and second side members extending substantially in the direction of vehicle travel and first and second cross members extending substantially perpendicular to the direction of vehicle travel. The first and second cross members are integral with the first and second side members such that the subframe is a unitary member. The first and second side members and the first and second cross members are further configured to receive first and second lower suspension control arms, first and second upper suspension control arms, and a portion of the steering linkage for the vehicle. The subframe may further be configured to receive a steering gear and one or more strut rods to provide fore/aft support to the subframe.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to vehicle suspensions and, in particular, to asubframe for use in an independent front suspension system.

2. Disclosure of Related Art

It is conventional in motor vehicles having independent frontsuspensions to incorporate a subframe to increase the strength of theaxle on which the suspension is employed. Conventional subframes used inheavy truck applications, however, have suffered from several drawbacks.First, most conventional subframes include numerous members that arecoupled together using bolts, welds, or other fastening means. Theassembly of these members into a single subframe makes dimensionalcontrol of mounting points for suspension and steering componentsrelatively difficult thereby increasing wear on the suspensioncomponents and joints among other drawbacks. The assembly also increasesthe time and cost required to produce the subframe. Second, conventionalsubframes have generally been unable to accommodate suspension controlelements and steering components to allow the building of a singlesuspension and steering subassembly. Third, conventional subframes arerelatively heavy and consume a relatively large amount of space.

There is thus a need for a subframe for motor vehicles that willminimize or eliminate one or more of the above-mentioned deficiencies.

SUMMARY OF THE INVENTION

The present invention provides a subframe for a motor vehicle and, inparticular, for heavy trucks.

A subframe in accordance with the present invention includes first andsecond side members. These side members may extend substantially in thedirection of vehicle travel. The subframe also includes first and secondcross members. The cross members may extend substantially perpendicularto the direction of vehicle travel. The first and second cross membersare integral with the first and second side members such that thesubframe is a unitary member. The first and second side members and thefirst and second cross members are further configured to receive firstand second lower suspension control arms and first and second uppersuspension control arms. The subframe may also be configured to receiveand support a portion of the steering linkage for the vehicle. Thesubframe may further be configured to receive one or more strut rods toprovide fore/aft support to the subframe. Finally, the subframe mayinclude a engine mount cross member integral with the first and secondside members and first and second cross members.

A subframe in accordance with the present invention has severaladvantages as compared to conventional subframes used in heavy truckapplications. First, because the members of the subframe are integralwith one another, there are no bolts, welds, or other fastenersrequired. As a result, assembly time and cost is reduced. Moreimportantly, better dimensional control of suspension and steeringmounting points is ensured. Second, the subframe allows relatively easymanufacture and production of a subassembly including many of theconventional suspension and steering components. Third, the subframe isrelatively light as compared to conventional subframes and requires lessspace.

These and other features and objects of this invention will becomeapparent to one skilled in the art from the following detaileddescription and the accompanying drawings illustrating features of thisinvention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vehicle frame having a suspension andsteering subassembly with a subframe in accordance with the presentinvention.

FIG. 2 is an exploded perspective view of the vehicle frame andsuspension and steering subassembly of FIG. 1.

FIG. 3 is a perspective view of a subframe in accordance with thepresent invention supporting a steering linkage.

FIG. 4 is a top plan view of the subframe of FIG. 3 supporting asteering linkage.

FIGS. 5 and 6 are perspective views of a first embodiment of a subframein accordance with the present invention.

FIG. 7 is a front plan view of the subframe of FIGS. 3 and 4reconfigured to support a steering gear.

FIG. 8 is a perspective view of a second embodiment of a subframe inaccordance with the present invention.

FIG. 9 is a perspective view of a third embodiment of a subframe inaccordance with the present invention mounted to a vehicle frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference numerals are usedto identify identical components in the various views, FIGS. 1-2illustrate a vehicle frame 20 to which is coupled a suspension andsteering subassembly 22 in accordance with the present invention. Theillustrated frame 20 and subassembly 22 are configured for use in heavytruck applications. It should be understood, however, that the presentinvention may find application in other types of vehicles.

Frame 20 is provided to support an engine (not shown), cab (not shown)and other components of a heavy truck. Frame 20 is conventional in theart and may be made from conventional metals and metal alloys such assteel. Frame 20 includes a pair of longitudinal rails 24, 26 extendingparallel to an axis 28 that extends in the direction of vehicle traveland in the longitudinal direction of the truck. Frame 20 also includes apair of reinforcement members 30, 32 and a cross-member 3A. Frame mayalso include a plurality of mounting brackets including brackets 38, 40,42.

Rails 24, 26 are provided to secure and align a cab on frame 20 and areconventional in the art. Rails 24, 26 are generally C-shaped incross-section and open toward one another. Rails 24, 26 may include aplurality of apertures configured to received bolts, screws, or otherfasteners to secure mounting brackets 38, 40, 42 to rails 24, 26.

Reinforcement members 30, 32 provide additional torsional stiffness toframe 20 and are conventional in the art. Members 30, 32 support, andare disposed below, rails 24, 26 respectively. Members 30, 32 aretubular in construction and are rectangular in cross-section in theillustrated embodiment. Members 30, 32 may be coupled to rails 24, 26using bolts, screws, welds, or other fastening means.

Cross-member 34 is provided to support the vehicle engine (not shown)and is also conventional in the art. Member 34 may be cast fromaluminum. Member 34 is fastened to reinforcement members 30, 32 usingbolts, screws, welds, or other fastening means and extend in a directionthat is generally transverse to axis 28 and the direction of vehicletravel.

Brackets 38, 40, 42 are provided to mount various components of thevehicle to frame 20 and are conventional in the art. Bracket 38 providesa mounting point for the vehicle engine. Brackets 40, 42 providemounting points for elements of subassembly 22. It will be understood bythose in the art that the number, shape, and configuration of brackets38, 40, 42 may vary depending upon the design requirements ofsubassembly 22 and other components of the vehicle.

Suspension and steering subassembly 22 provides an independent frontsuspension and steering system for the vehicle. Subassembly 22 mayinclude upper suspension control arms 44, 46, lower suspension controlarms 48, 50, shock/spring units 52, 54, strut rods 56, 58, a steeringlinkage 60, and a subframe 62 in accordance with the present invention.

Upper and lower suspension control arms 44, 46, 48, 50 provide a meansfor mounting steering knuckles (not shown) on either side of the vehicleand adjustment of the vehicle wheels (not shown). Arms 48, 50 alsoprovide mounting points for shock/spring units 52, 54. Arms 44, 46, 48,50 are conventional in the art and may be made from a variety ofconventional metals and metal alloys. In the illustrated embodiment,each of upper control arms 44, 46 includes a bushing 64 from which agenerally semi-circular flange 66 extends. Bushing 64 is received bysubframe 62 as described in greater detail hereinbelow. Flange 66includes an aperture 68 configured to allow one of shock/spring units52, 54 to extend therethrough and another aperture 70 through whichflange 66 may be coupled to a steering knuckle (not shown). Each oflower suspension control arms 48, 50 is generally A-shaped including apair of legs 72, 74 and a cross-member 76. A bushing 78 is disposed atthe inboard end of each leg 72, 74 and is received by subframe 62 asdescribed hereinbelow. Legs 72, 74 define a mounting member 80 at theoutboard intersection of legs 72, 74 for mounting one of shock/springunits 52, 54 and a steering knuckle (not shown). It should be understoodby those of skill in the art that the size, shape, and configuration ofarms 44, 46, 48, 50 may vary depending upon design requirementsassociated with vehicle and its components without departing from thespirit of the present invention.

Shock/spring units 52, 54 are provided to cushion the ride of vehicle.Units 52, 54 are conventional in the art any may include a shock 82 andan air spring 84. Shock 82 is supported at one end by mounting member 80of lower suspension control arm 50. The other end of shock 82 extendsinto a bladder of air spring 84. Air spring 84 is disposed againstmounting bracket 42 of frame 20.

Strut rods 56, 58 act to stabilize subframe 62 under brake loads byproviding additional fore/aft support to subframe 62 and also minimizingstress due to helical loading from frame 20. Rods 56, 58 areconventional in the art. Rods 56, 58 are pivotally mounted to frame 20at one end and to subframe 62 at the other end using bushings 86, rubberisolators or other ball style joints designed to allow pivotal motion,but limited radial travel.

Steering linkage 60 provides directional control of the vehicle wheels(not shown) responsive to driver control of the steering wheel (notshown) by transferring motion of the steering gear output shaft (notshown) to the vehicle wheels. Linkage 60 is conventional in the art.Referring to FIGS. 3 and 4, linkage 60 may include outer tie rods 88,90, an idler arm 92, a cross link 94, and a bell crank 96. Tie rods 88,90 are connected to the steering knuckles (not shown) at their outboardends and to idler arm 92 and bell crank 96, respectively, at theirinboard ends. Cross link 94 couples idler arm 92 and bell crank 96. Bellcrank 96 is in turn coupled to a steering gear output shaft (not shown)by a drag link (not shown). Crank 96 rotates responsive to rotation ofthe steering gear output shaft and causes corresponding movement in link94, arm 92, and tie rods 88, 90 to turn the vehicle wheels (not shown).

Referring now to FIGS. 5-6, a subframe 62 in accordance with oneembodiment of the present invention will be described. Subframe 62 isprovided to increase the transverse strength of the axle on whichsubassembly 22 is employed and may be cast from aluminum. Subframe 62 isunitary in construction and includes a pair of side members 98, 100 anda pair of cross members 102, 104.

Side members 98, 100 extend generally parallel to axis 28 when subframe62 is mounted to frame 20. Each of members 98, 100 includes a pair ofmounting flanges 106, 108 and 110, 112, respectively, extendingtherefrom in a direction generally perpendicular to axis 28. Flanges106, 108 and 110, 112 are configured to receive corresponding uppercontrol arms 44, 46 (and particularly bushings 64 of arms 44, 46)therebetween and include apertures 114 configured to receive bolts,screws, or other fasteners to pivotally couple upper suspension controlarms 44, 46 to subframe 62. Members 98, 100 may also include mountingflanges 114, 116 and 118, 120, respectively, extending therefrom in adirection generally parallel to axis 28. Referring to FIG. 1, flanges114, 116 and 118, 120 are configured to receive bolts, screws, or otherfasteners to couple subframe 62 to mounting brackets 40, 42 of frame 20.

Cross members 102, 104 extend generally perpendicular to axis 28 whensubframe 62 is mounted to frame 20. Each of cross members 102, 104 isintegral with each of side members 98, 100. In the illustratedembodiment, each cross member 102, 104 includes a central portion, 122,124, respectively, and two end portions, 126, 128 and 130, 132,respectively, that extend upwardly at an angle from portions 122, 124 toconnect cross members 102, 104 to side members 98, 100. Each of endportions 126, 128, 130, 132 define means for mounting lower suspensioncontrol arms 48, 50 to subframe 62. In the illustrated embodiment, themounting means comprise C-shaped mounting members 134, 136, 138, 140extending outwardly from portions 126, 128, 130, 132 of members 102, 104in a direction generally parallel to axis 28. Members 134, 136, 138, 140are sized to receive bushings 78 of arms 48, 50 and include apertures142 configured to receive bolts, screws, or other fasteners used tocouple bushings 78 to members 134, 136, 138, 140. Members 138, 140 maythemselves also include means for mounting strut rods 56, 58 (best shownin FIG. 1) to subframe 62. In particular, each of members 138, 140 mayinclude a pair of mounting flanges 144, 146 and 148, 150, respectively,extending from members 138, 140 in a direction generally parallel toaxis 28. Flanges 144, 146 and 148, 150 are configured to receivebushings 86 of rods 56, 58 therebetween and include apertures configuredto receive bolts, screws, or other fasteners used to pivotally couplestrut rods 56, 58 to subframe 62.

Side members 98, 100 and cross member 102 may be further configured toreceive steering linkage 60. In particular, members 98, 100, 102 maydefine pairs of spaced mounting plates 152, 154, 156, 158 configured toreceive portions of steering linkage 60. Referring to FIGS. 3 and 4,plates 152, 154 may be configured to receive idler arm 92 while plates156, 158 may be configured to receive bell crank 96. Plates 152, 154,156, 158 include apertures 160 configured to receive a shaft or pin (notshown) on which arm 92 and crank 96, respectively, may be pivotallymounted.

Referring to FIG. 7, in a further enhancement of the present invention,subframe 62 may be configured to receive a steering gear 162 and thesteering linkage 60 may be modified by replacing bell crank 96 with apitman arm 164. The incorporation of steering gear 162 is advantageousbecause it eliminates the need for bell crank 96 and a separate draglink connecting crank 96 to the steering gear. The pitman arm 164connects linkage 60 to the steering column through steering gear 162 andmoves linkage 60 left or right.

A subframe 62 in accordance with the present invention represents asignificant improvement as compared to conventional subframes used inheavy truck applications. Because the side members 98, 100, crossmembers 102, 104, and mounting features on subframe 62 are all integralwith one another, there are no bolts, welds, or other fasteners requiredto build subframe 62. As a result, assembly time and cost is reduced.More importantly, however, better dimensional control of suspension andsteering mounting points is ensured as tolerance stackups are limited.The subframe 62 also allows relatively easy manufacture and productionof a subassembly 22 including many of the conventional suspension andsteering components. Further, the subframe 62 is relatively light ascompared to conventional subframes, requires less space, and allows thevehicle engine to be mounted lower to the ground, thereby increasing cabspace.

It should be understood by those of skill in the art that the size,shape, and configuration of a subframe in accordance with the presentinvention may vary depending upon the design requirements associatedwith the frame, suspension, steering, and other components of thevehicle on which the subframe is to be mounted. As such, the embodimentillustrated in FIGS. 5-6 and described hereinabove is not meant to limitthe scope of the claimed invention. Rather, a subframe in accordancewith the present invention may assume a variety of forms-one example ofwhich is illustrated in FIG. 8.

Referring now to FIG. 8, a second embodiment of a subframe 166 inaccordance with the present invention will be described. Like subframe62, subframe 166 includes a pair of side members 168, 170 and a pair ofcross members 172, 174.

Side members 168, 170 extend generally parallel to axis 28 when subframe166 is mounted to frame 20 and are located inboard of the outboard endsof cross members 172, 174. Each of members 168, 170 includes a pair ofintersecting support arms 176, 178 and 180, 182, respectively, extendingtherefrom in a generally outboard direction. Arms 176, 178 and 180, 182,respectively, include axially extending apertures 184 at the point ofintersection configured to receive a screw, bolt, or other fastener tocouple upper suspension control arms (not shown) thereto and allowpivoting motion of upper suspension control arms. Each of members 168,170 also includes a pair of mounting flanges 186, 188 and 190, 192,respectively, extending therefrom in a direction generally perpendicularto axis. Flanges 186, 188 and 190, 192, together with the outboard endsof cross members 172, 174, are configured to receive corresponding lowersuspension control arms (and particularly bushings of the arm arms-notshown) therebetween and include apertures 194 configured to receivebolts, screws, or other fasteners to couple the lower suspension controlarms to subframe 166.

Cross members 172, 174 extend generally perpendicular to axis 28 whensubframe 166 is mounted to frame 20. Each of cross members 172, 174 isintegral with each of side members 168, 170. In the illustratedembodiment, each cross member 172, 174 includes a central portion 196,198, respectively, and two end portions 200, 202 and 204, 206,respectively, that extend upwardly at an angle from portions 196, 198.End portions 200, 202 may define mounting flanges 208, 210,respectively, extending therefrom in a direction generally perpendicularto axis 28. Flanges 208, 210 are configured to receive bolts, screws, orother fasteners to couple subframe 166 to mounting brackets 40, 42 offrame 20 (not shown). It should be understood that end portions 204, 206may define similar mounting flanges (not shown).

Although not illustrated in the present embodiment, it should beunderstood that member 174 may also define means for mounting strut rods56, 58 to subframe 166 in a manner similar to members 104 of subframe 62(see FIGS. 3 and 4). Also, side members 168, 170 and another of crossmember 172 may be further configured to receive steering linkage 60. Inparticular, members 168, 170, 172 may define pairs of mounting platesconfigured to receive portions of steering linkage 60 in a mannersimilar to subframe 62.

Referring now to FIG. 9, a third embodiment of a subframe 212 inaccordance with the present invention will be described. Subframe 212 issubstantially similar to subframe 62. Subframe 212, however, includes across member 214 that is integral with the other components of subframe212. As illustrated in FIG. 9, member 214 is provided to support thevehicle engine and may take the place of cross member 34 of frame 20shown in FIGS. 1-2. Member 214 extends generally transverse to axis 28.It should be understood that the size, shape, and configuration ofmember 214 may vary depending upon design requirements associated withthe vehicle engine and frame 20.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it is well understood bythose skilled in the art that various changes and modifications can bemade in the invention without departing from the spirit and scope of theinvention.

1. (canceled)
 2. The subframe of claim 24 wherein said first and secondcross members are configured to receive said first and second lowersuspension control arms.
 3. The subframe of claim 24 wherein said firstand second side members are configured to receive said first and secondupper suspension control arms.
 4. The subframe of claim 24, furthercomprising a third cross member integral with said first and second sidemembers, said third cross member configured to support an engine of saidvehicle.
 5. The subframe of claim 24 wherein said first cross member isconfigured to receive a strut rod.
 6. The subframe of claim 24 whereinsaid first and second side members and said first and second crossmembers are configured to receive a steering linkage. 7-10. (canceled)11. The subframe of claim 6 wherein said first and second side membersand said first and second cross members are configured to receive anidler arm of said steering linkage.
 12. The subframe of claim 24 whereinsaid first and second side members and said first and second crossmembers are configured to receive a steering gear.
 13. (canceled) 14.The vehicle subassembly of claim 17 wherein said first and second crossmembers are configured to receive said first and second lower suspensioncontrol arms.
 15. The vehicle subassembly of claim 17 wherein said firstand second side members are configured to receive said first and secondupper suspension control arms.
 16. The vehicle subassembly of claim 17wherein said subframe includes a third cross member integral with saidfirst and second side members, said third cross member configured tosupport an engine of said vehicle.
 17. A vehicle subassembly,comprising: a subframe having first and second side members; and, firstand second cross members, each of said first and second cross membersconnected to said first and second side members; first and second lowersuspension control arms coupled to said subframe; first and second uppersuspension control arms coupled to said subframe; and, a strut rodhaving a first end coupled to said subframe and a second end coupled toa vehicle frame.
 18. The vehicle subassembly of claim 17, furthercomprising a steering linkage coupled to said subframe.
 19. (canceled)20. The vehicle subassembly of claim 17, further comprising a steeringgear mounted on said subframe.
 21. The vehicle subassembly of claim 18,wherein said first and second side members and said first and secondcross members are configured to receive an idler arm of said steeringlinkage.
 22. The vehicle subassembly of claim 17 wherein said second endof said strut rod is coupled to one of first and second C-shapedlongitudinal frame rails of said frame.
 23. The vehicle subassembly ofclaim 17 wherein each of said first and second cross members is integralwith said first and second side members.
 24. A subframe for a motorvehicle, comprising: first and second side members extending generallyparallel to an axis extending in a longitudinal direction of saidvehicle; and, first and second cross members, each of said first andsecond cross members connected to said first and second side memberswherein said first and second side members and said first and secondcross members are configured to receive first and second lowersuspension control arms and first and second upper suspension controlarms and said first and second lower suspension control arms and saidfirst and second upper suspension control arms form an independent frontsuspension for said vehicle.
 25. The subframe of claim 24 wherein eachof said first and second cross members is integral with said first andsecond side members.